Significance of different probability distributions in flood frequency analysis of Brahmani-Baitarani River Basin, India

Appropriate flood management in a basin requires analysis of peak discharge prediction and flood frequency. The main aim is to find the most suitable distribution model at various gauges for the entire Brahmani-Baitarani River basin for proper flood management. Daily flow data lengths ranging from 23 to 46 years for multiple gauges are obtained from the Central Water Commission. The present analysis employs the Generalized Extreme Value (GEV), Gumbel Max, Log-Pearson III (LP3), and Lognormal models to estimate the flood quantiles of various return periods. The L-moment, Method of Moment, and Maximum Likelihood Method are applied to estimate the model parameters. Goodness-of-fit tests, accuracy measures, and relative scoring indicated LP3 as the best-fit model, followed by GEV. The results indicated that floods with return periods of longer than 100 years can be considered for designing hydraulic structures in the upper reaches of the basin, whereas floods with return periods of longer than 50 years can be considered for the lower reaches. Significant constraints in the present study involve a limited number of gauges and their varied record lengths in this extensive basin. The findings of this study can be used in water resource planning, flood hazard mapping, and the design of hydraulic structures within similar catchments.